A ferry in San Francisco recently crashed into the docks. (@verytiffany/Twitter)

SAN FRANCISCO -- The U.S. Coast Guard is investigating what caused a ferry boat to crash twice into docks at San Francisco's famed Ferry Building, slightly injuring two people aboard.

Coast Guard spokesman Chris Shih says investigators are looking into mechanical issues and other factors that led to Friday's crash. The agency regularly inspects the ferries.

A Golden Gate Ferry spokeswoman says the boat was travelling from Larkspur and carrying 53 passengers when it struck an outer berth before bumping into another dock.

The vessel's hull was damaged when it struck the concrete promenade and knocked a guardrail. The Coast Guard says there were reports of two minor injuries that didn't require treatment beyond first aid.

Witness Tiffany Dennis says the crash set off panic among a crowd of people dining and shopping at the waterfront attraction.

Ferry crash @ ferry building @KTVU @kron4news pic.twitter.com/o8JQK1e8yq

Ferry damage �� pic.twitter.com/SkcjTYbTAX

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